Johannesburg: South African police arrested 59 people and the army was called in overnight to quell post-election protests in a Johannesburg slum, police and media said on Saturday, as the ANC government clamped down on disorder following its victory at the polls.

Police on Friday used rubber bullets and stun grenades to disperse protestors in the impoverished black township of Alexandra who had burned tyres and barricaded roads, spokesman Brigadier Neville Malila said.

Alexandra was “calm this morning,” he said, adding that “security forces” remained in the area.

The South African Press Association earlier reported the army had been called in overnight to restore calm, quoting the premier of Gauteng province, Nomvula Mokonyane.

Although the ruling African National Congress remains popular with South Africa’s black majority after dismantling the apartheid system is 1994, there is rising discontent among the millions stuck in grinding poverty and without access to running water or electricity.

The ANC won the 2014 national election with 62.16 per cent of the votes, according to a provisional tally.

The official numbers are due to be announced later on Saturday and President Jacob Zuma is expected to address the nation at 1600 GMT.

Following the vote, as many as 400 people gathered on Friday outside a court in Alexandra to burn tyres and demand the release of other protestors arrested a day earlier, police spokesman Malila said.

On Thursday, at least 39 people were arrested after an electoral commission office was torched in Alexandra. Both groups of those detained are due to appear in court on Monday.

By calling in the army, the African National Congress government is taking a harder tack against public unrest than it has in the recent past.

When violent labour unrest swept through the country’s platinum belt in 2012, the government put the army on standby but did not dispatch it.

Burdened with sluggish economic growth and damaging strikes in his first term, the scandal-plagued Zuma is at pains to soothe investor concerns about Africa’s most sophisticated economy and push through pro-business reforms.

Over the last year he has devoted less and less time to the wishes of unions, whose long walkouts have hit confidence in the economy.

Zuma hinted this week that the ANC needed to take a more pro-business stance, accusing the main platinum union of irresponsibility for dragging out a four-month wage strike.